Electric source circuit for camera

Abstract

An electric source circuit for a camera in which the voltage of a power source is automatically applied to the exposure control and display circuit of a camera when the electronic flash is fully charged. A first switch circuit is operatively coupled between a power source and the exposure control and display circuit. A photometric switch for controlling the conduction and non-conduction of the first switching circuit is coupled in parallel with the second switching circuit. The second switching circuit is coupled to detect when the electronic flash mounted on the camera is fully charged. A third switching circuit can be provided for activating an indicating device such as an LED or piezoelectric transducer.

What is claimed is: 
     
       1. In an electronic source circuit for a camera having in the viewfinder thereof a display element which is activated upon the completion of charging of an electronic flash unit on the camera when a photometric switch is manually closed to connect a power source to the exposure control and display circuit of the camera, the improvement comprising: first switching circuit means coupled between the power source and the exposure control and display circuit, said switching circuit means being rendered conductive upon closing of the photometric switch to connect the power source to the exposure control and display circuit; and   second switching circuit means, connected in parallel with the photometric switch and rendered conducting in response to the charge voltage upon completion of the charging of the electronic flash unit, for connecting the power source to the exposure control and display circuit even when the photometric switch is open.   
     
     
       2. The improvement of claim 1 further comprising third switching circuit means coupled to a control input of the exposure control and display circuit and responsive to the charge voltage upon completion of the charging of the electronic flash unit to apply a control signal to said control input when the power source is connected to the exposure control and display circuit. 
     
     
       3. An electric source circuit for a camera comprising: an electric source;   a first transistor having an emitter coupled to a first terminal of said power source;   a first resistor coupled between said emitter and a base of said first transistor;   a photometric switch, a first terminal of said photometric switch being coupled to a second terminal of said power source;   a second resistor having a first terminal coupled to said base of said first transistor and a second terminal coupled to a second terminal of said photometric switch;   a second transistor of a conductivity type opposite that of said first transistor, said second transistor having a collector coupled to said second terminal of said photometric switch and an emitter coupled to said second terminal of said power source; and   a third resistor having a first terminal coupled to said base of said second transistor and a second terminal adapted to be coupled to an active terminal of an electronic flash unit, a collector of said first transistor and said second terminal of said power source being coupled to an exposure control and display circuit in said camera.   
     
     
       4. The electric source circuit of claim 3 further comprising a third transistor of the same conductivity type as said second transistor, said third transistor having an emitter coupled to said second terminal of said power source, a base coupled to said base of said second transistor, and a collector coupled to a control input of said exposure control and display circuit for operating an indicating device therein and a fifth resistor having a first terminal coupled to said collector of said third transistor and a second terminal coupled to said collector of said first transistor.